Long-Term Debt (Narrative) (Details)		12 Months Ended
	Mar. 16, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 30, 2017 USD ($)	Mar. 15, 2017 USD ($)	Dec. 31, 2015 USD ($)
Maximum [Member]
Line of Credit Facility [Line Items]
Interest rate per annum		4.60%
Minimum [Member]
Line of Credit Facility [Line Items]
Interest rate per annum		4.16%
F&M Bank [Member]
Line of Credit Facility [Line Items]
Loans outstanding		$ 2,400,000			$ 869,000
Prosperity Bank [Member]
Line of Credit Facility [Line Items]
Credit facility current borrowing capacity		$ 3,000,000
Rate above prime		0.50%
Credit facility maturity date		Jul. 31, 2018
Prosperity Bank [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Credit facility current borrowing capacity	$ 1,250,000			$ 3,000,000
Maximum line of credit			$ 40,000,000
Loans outstanding			$ 0
Interest rate	4.50%
Prosperity Bank [Member] | Maximum [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Funded debt to EBITDA	3.5
Prosperity Bank [Member] | Minimum [Member] | Subsequent Event [Member]
Line of Credit Facility [Line Items]
Current ratio	1
Interest coverage	3.0
Prosperity Bank [Member] | Loans And Letters Of Credit [Member]
Line of Credit Facility [Line Items]
Maximum line of credit		$ 40,000,000